When a knee joint suffers knee osteoarthritis, rheumatoid arthritis, or bone tumors, or suffers external injury or the like, the part subject to joint damage at the tips of the femur and tibia is resected, and those parts are replaced with an artificial joint. This artificial knee joint, as conventionally seen, comprises a combination of a femur component, which has two condyles of medial and lateral, and a tibia component, which has a joint plate that bears these two condyles and allows them to rotate; and it is desirous that artificial knee joints that are comprised of such condyles and joint plates preferably be movable similarly to a biogenic knee joint.
The femur and tibia are connected by numerous ligaments, and extension and flexion of them are made by tensioning and relaxing these ligaments. It is particularly desirable that when tensioning occurs tension be the same when in the extension position and when in the flexion position, and it is also desirable that flexion movement be smooth accompanying no pain. Also, since Japanese people often sit with their legs folded beneath them, it is necessary that deep flexion is possible. With these situations in mind, Patent Literature 1, listed below, proposes a bone resection jig that sets a bone resection range after confirming that tension is the same in the extension position and in the flexion position.
However, the invention of this prior art checks (measures) the tension of ligaments in both extension and flexion positions; accordingly, the operation is troublesome, and it requires a longer surgical time. Further, the constitution is complex, and it includes many moving parts and adjustment parts, and further it requires numerous operation steps that are difficult and require proficiency. In addition, it is heavy and expensive.